How to add floating particles to a fluid simulation?
I have come across this question myself and have not found an easy way to do it. I'm sure my answer isn't the best, but I hope it helps :D

Here we go:


Bake your fluid simulation
Create a plane and subdivide it a few times.
Shrinkwrap the object to your fluid simulation using the 'project' option.

Then use object constraints to bind the 'floating' object to the plane you just created on the z-axis. Remember to create a vertex group on the plane and assign it to the constraint.
Constrain the plane to the floating object on the x-axis and y-axis
Tweak the offset to get the correct depth




Best of luck with your project and I hope I helped,

BFB